Date: Mon, 07 May 2001 12:37:22 -0700 (PDT) From: John Baldwin <jhb@FreeBSD.org> To: Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp> Cc: current@FreeBSD.org Subject: RE: select(2) converted to use a condition variable, and optimis Message-ID: <XFMail.010507123722.jhb@FreeBSD.org> In-Reply-To: <200105060731.f467V4g13184@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp>
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On 06-May-01 Seigo Tanimura wrote:
> As conversion of select(2) from msleep(9) to a condition variable is
> in the SMPng TODO list, I have done that task.
>
> Also, we do not have to lock a process in order to evaluate the result
> of {sel,poll}scan() and the remaining time of {select,poll}(2). It
> should be enough to do those pieces of work first, followed by locking
> a process and wait for a condition variable or selwakeup().
You need the lock when clearing the bit in p_flag. That is why the proc locks
are there, so all those proc locks need to stay. When you clear a bit, you are
writing all the bits, so you need to ensure that you can atomically
read/modify/write all the bits in p_flag, hence the need for the proc lock.
Please back out the changes to not lock the process around the p_flag change.
The rest of the patch looks ok, though I'd like to review the updated version
before it is committed. Thanks.
> Those changes are in the patch at:
>
> http://people.FreeBSD.org/~tanimura/patches/selectopt.diff
--
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